Remove the postings highlighter and make unified the default highlighter choice

buildSrc/src/main/resources/checkstyle_suppressions.xml

@@ -16,7 +16,6 @@
   <!-- Hopefully temporary suppression of LineLength on files that don't pass it. We should remove these when we the
     files start to pass. -->
   <suppress files="client[/\\]rest[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]client[/\\]HeapBufferedAsyncResponseConsumerTests.java" checks="LineLength" />
-  <suppress files="core[/\\]src[/\\]main[/\\]java[/\\]org[/\\]apache[/\\]lucene[/\\]search[/\\]postingshighlight[/\\]CustomPostingsHighlighter.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]main[/\\]java[/\\]org[/\\]apache[/\\]lucene[/\\]search[/\\]vectorhighlight[/\\]CustomFieldQuery.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]main[/\\]java[/\\]org[/\\]elasticsearch[/\\]action[/\\]Action.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]main[/\\]java[/\\]org[/\\]elasticsearch[/\\]action[/\\]ActionRequestBuilder.java" checks="LineLength" />
@@ -428,7 +427,6 @@
   <suppress files="core[/\\]src[/\\]main[/\\]java[/\\]org[/\\]elasticsearch[/\\]threadpool[/\\]ThreadPool.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]main[/\\]java[/\\]org[/\\]elasticsearch[/\\]tribe[/\\]TribeService.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]apache[/\\]lucene[/\\]queries[/\\]BlendedTermQueryTests.java" checks="LineLength" />
-  <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]apache[/\\]lucene[/\\]search[/\\]postingshighlight[/\\]CustomPostingsHighlighterTests.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]VersionTests.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]action[/\\]RejectionActionIT.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]action[/\\]admin[/\\]HotThreadsIT.java" checks="LineLength" />

core/src/main/java/org/apache/lucene/search/uhighlight/CustomPassageFormatter.java

@@ -20,7 +20,6 @@
 package org.apache.lucene.search.uhighlight;
 
 import org.apache.lucene.search.highlight.Encoder;
-import org.apache.lucene.search.highlight.Snippet;
 import org.elasticsearch.search.fetch.subphase.highlight.HighlightUtils;
 
 /**

core/src/main/java/org/apache/lucene/search/uhighlight/CustomUnifiedHighlighter.java

@@ -27,7 +27,6 @@
 import org.apache.lucene.search.PrefixQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TermQuery;
-import org.apache.lucene.search.highlight.Snippet;
 import org.apache.lucene.search.spans.SpanMultiTermQueryWrapper;
 import org.apache.lucene.search.spans.SpanNearQuery;
 import org.apache.lucene.search.spans.SpanOrQuery;

core/src/main/java/org/apache/lucene/search/highlight/Snippet.java → core/src/main/java/org/apache/lucene/search/uhighlight/Snippet.java

@@ -17,11 +17,11 @@
  * under the License.
  */
 
-package org.apache.lucene.search.highlight;
+package org.apache.lucene.search.uhighlight;
 
 /**
  * Represents a scored highlighted snippet.
- * It's our own arbitrary object that we get back from the postings highlighter when highlighting a document.
+ * It's our own arbitrary object that we get back from the unified highlighter when highlighting a document.
  * Every snippet contains its formatted text and its score.
  * The score is needed in case we want to sort snippets by score, they get sorted by position in the text by default.
  */

core/src/main/java/org/elasticsearch/search/SearchModule.java

@@ -229,7 +229,6 @@
 import org.elasticsearch.search.fetch.subphase.highlight.HighlightPhase;
 import org.elasticsearch.search.fetch.subphase.highlight.Highlighter;
 import org.elasticsearch.search.fetch.subphase.highlight.PlainHighlighter;
-import org.elasticsearch.search.fetch.subphase.highlight.PostingsHighlighter;
 import org.elasticsearch.search.fetch.subphase.highlight.UnifiedHighlighter;
 import org.elasticsearch.search.rescore.QueryRescorerBuilder;
 import org.elasticsearch.search.rescore.RescoreBuilder;
@@ -574,7 +573,6 @@ private Map<String, Highlighter> setupHighlighters(Settings settings, List<Searc
         NamedRegistry<Highlighter> highlighters = new NamedRegistry<>("highlighter");
         highlighters.register("fvh",  new FastVectorHighlighter(settings));
         highlighters.register("plain", new PlainHighlighter());
-        highlighters.register("postings", new PostingsHighlighter());
         highlighters.register("unified", new UnifiedHighlighter());
         highlighters.extractAndRegister(plugins, SearchPlugin::getHighlighters);
 

core/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/AbstractHighlighterBuilder.java

@@ -262,8 +262,8 @@ public Integer numOfFragments() {
 
     /**
      * Set type of highlighter to use. Out of the box supported types
-     * are <tt>plain</tt>, <tt>fvh</tt> and <tt>postings</tt>.
-     * The default option selected is dependent on the mappings defined for your index.
+     * are <tt>unified</tt>, <tt>plain</tt> and <tt>fvj</tt>.
+     * Defaults to <tt>unified</tt>.
      * Details of the different highlighter types are covered in the reference guide.
      */
     @SuppressWarnings("unchecked")

core/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/FastVectorHighlighter.java

@@ -50,7 +50,6 @@
 import java.util.Map;
 
 public class FastVectorHighlighter implements Highlighter {
-
     private static final BoundaryScanner DEFAULT_SIMPLE_BOUNDARY_SCANNER = new SimpleBoundaryScanner();
     private static final BoundaryScanner DEFAULT_SENTENCE_BOUNDARY_SCANNER =
         new BreakIteratorBoundaryScanner(BreakIterator.getSentenceInstance(Locale.ROOT));

core/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/HighlightPhase.java

@@ -39,8 +39,6 @@
 import java.util.Map;
 
 public class HighlightPhase extends AbstractComponent implements FetchSubPhase {
-    private static final List<String> STANDARD_HIGHLIGHTERS_BY_PRECEDENCE = Arrays.asList("fvh", "postings", "plain");
-
     private final Map<String, Highlighter> highlighters;
 
     public HighlightPhase(Settings settings, Map<String, Highlighter> highlighters) {
@@ -94,13 +92,7 @@ public void hitExecute(SearchContext context, HitContext hitContext) {
                 }
                 String highlighterType = field.fieldOptions().highlighterType();
                 if (highlighterType == null) {
-                    for(String highlighterCandidate : STANDARD_HIGHLIGHTERS_BY_PRECEDENCE) {
-                        if (highlighters.get(highlighterCandidate).canHighlight(fieldMapper)) {
-                            highlighterType = highlighterCandidate;
-                            break;
-                        }
-                    }
-                    assert highlighterType != null;
+                    highlighterType = "unified";
                 }
                 Highlighter highlighter = highlighters.get(highlighterType);
                 if (highlighter == null) {

core/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/HighlightUtils.java

@@ -35,7 +35,7 @@
 
 public final class HighlightUtils {
 
-    //U+2029 PARAGRAPH SEPARATOR (PS): each value holds a discrete passage for highlighting (postings highlighter)
+    //U+2029 PARAGRAPH SEPARATOR (PS): each value holds a discrete passage for highlighting (unified highlighter)
     public static final char PARAGRAPH_SEPARATOR = 8233;
     public static final char NULL_SEPARATOR = '\u0000';
 

core/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/PlainHighlighter.java

@@ -49,7 +49,6 @@
 import java.util.Map;
 
 public class PlainHighlighter implements Highlighter {
-
     private static final String CACHE_KEY = "highlight-plain";
 
     @Override